Reed switch manufacture

ABSTRACT

A method for precisely positioning the conductive elements of an electrical device within a sealed enclosure. As applied to the manufacture of high accuracy reed switches, the method includes the steps of initially disposing the contact reed blades (reeds) of the switch in the relative position desired in the finished product; rigidly joining the reeds within a region adjacent the respective contact areas to maintain the established geometry; sealing the reeds within an enclosure while joined as aforesaid to retain the established relative position; and thereafter eliminating the connection joining the reeds within the sealed enclosure to provide a completed switch with contacts permanently and precisely spaced in accordance with the pre-established relative position.

United States Patent [191 Hill et a1.

[ REED SWITCH MANUFACTURE [75] Inventors: John Hill, Bickley; HenrykTurczanskl, Beckenham, both of England [73] Assignee: Comtelco (U.K.)Limited, Tonbridge, Kent, England [22] Filed: Dec. 11, 1973 [21] Appl.No.: 423,735

[30] Foreign Application Priority Data Feb. 6, 1973 United Kingdom5839/73 [52] [1.8. CI 29/622; 29/418 [51] Int. Cl 1323p 17/00 [58] Fieldof Search 29/622, 628, 203, 418, 29/623; 335/151, 152, 153

[56] References Cited I UNITED STATES PATENTS 2,696,543 12/1954 Ellwood200/165 2,978,556 4/1961 Lohs et al. 335/152 3,284,876 11/1966 Buttel29/622 3,345,593 10/1967 Grengg 29/404 3,369,291 2/1968 Shaffer et a1.29/622 3,432,282 3/1969 Schulz 65/32 3,443,312 5/1969 Moriyama et a129/622 3,550,268 12/1970 Santi 29/622 TIMER #98 ME LTING CURRENT SOURCE[4 1 May 20, 1975 3,568,310 3/1971 Neuber 29/622 FOREIGN PATENTS ORAPPLICATIONS 1,513,486 10/1969 Germany 29/623 1.184.015 12/1964 Germany29/622 Primary Examiner--C. W. Lanham Assistant Examiner-James R. DuzanAttorney, Agent, or Firm-Weingarten, Matham & Schurgin [57] ABSTRACT Amethod for precisely positioning the conductive elements of anelectrical device within a sealed enclosure. As applied to themanufacture of high accuracy reed switches, the method includes thesteps of initially disposing the contact reed blades (reeds) of theswitch in the relative position desired in the finished product; rigidlyjoining the reeds within a region adjacent the respective contact areasto maintain the established geometry; sealing the reeds within anenclosure while joined as aforesaid to retain the established relativeposition; and thereafter eliminating the connection joining the reedswithin the sealed enclosure to provide a completed switch with contactspermanently and precisely spaced in accordance with the pre-establishedrelative position.

11 Claims, 13 Drawing Figures PATENIED RAYZOIHIS SHEEI 2 BF 3 ANNEALING'CURRENT SOURCE TIMER MELTING CURRENT SOURCE REED SWITCH MANUFACTUREFIELD OF THE INVENTION The present invention relates in general to amethod for precisely positioning and assembling the component parts ofan electrical device, and more particularly concerns a method for theprecise and uniform placement of electrical elements in electricaldevices such as reed switches, mercury wetted sealed contacts, neonlamps, and multiple contact encapsulated switches.

BACKGROUND OF THE INVENTION The invention, while applicable to a widevariety of electrical devices in which contacts must be orientedprecisely with respect to each other within an enclosure for requisiteaccuracy, stability and long life, the principles and objects of thisinvention will be fully explained with specific reference to theefficient, low cost manufacture of high quality reed switchesheremctically sealed in glass or comparable materials.

The course of development of reed switches is de scribed in detail in anarticle entitled Development of Reed Switches and Relays" by O. M.Hovgaard and G. E. Perreault, Bell System Technical Journal, Vol. 34,No. 2. March l955, pp. 309 33?.. Typical prior methods for assemblingreed swithces are described in E. L. Pityo, U.S. Pat. No. 3,537,276,entitled Method of and Apparatus for Producing Magnetic Reed Switches,

dated Nov. 3, 1970, and in P. M. Zollman, US. Pat.

No. 3,628,242, entitled Manufacture of Electrical Switches, dated Dec.2t, 1971.

More specifically the Pityo patent discloses a fabrica tion technique inwhich a pair of reed blades are each held by a respective jaw mechanismwithin a glass sleeve disposed around the blades. The reed blades arecaused to engage, or latched to one another by an applied magneticfield, one jaw is released and the confronting unsecured end of theglass sleeve sealed to the associated lead portion of the reed blade.Thereafter the magnetic latching force is removed, the unsealed reedblade is displaced by a predetermined amount to define the desired gapbetween the contacts, and this reed blade is then sealed to theassociated end of the glass envelope to complete the assembly. Thetechnique proposed by Zollman is similar and employes a pair of reedblades magnetically held in overlapping relationship by a jaw affixed toone of the reed blades. A glass sleeve is installed over themagnetically held reed blades and the end of the glass adjacent theunsecured reed blade is sealed to this reed blade. The magnetic force isthen removed and the second reed blade displaced laterally from thefirst by a predetermined amount to establish the contact gap. Thedisplaced reed blade is then sealed to the glass sleeve to complete thedevice.

The teachings of both Pityo and Zollman necessarily require thefabrication and utilization of assembly machines which are inherentlycomplex, both mechanically and electrically, and require highly skilledlabor to maintain production efficiency and economy. Both combine thefunctions of accurately positioning the switch contact reed blades andsealing them into the glass envelope. Resultantly, inaccuraciesareintroduced due to expansion as positioning mechanisms become heatedin the course of sealing the glass envelopes.

German Pat. No. l,l 84,015 published Dec. 23, I964 discloses amanufacturing technique whereby the reed blades initially constituteintegral central portions of a generally open rectangular metal frame.The entire frame is first placed in a press which crimps the structureand brings the contact portions into predetermined alignment to definethe contact gap. A glass enclosure is slipped over and sealed to theaforesaid reed blade portions while still integral with the frame and ina final step, the exterior portions of the frame are cut away, leaving acompleted reed switch. During the sealing step the inner confrontingends of the blades are free; therefore, as set forth above withreference to the prior Pityo and Zollman patents, distortion of theblades due to expansion and contraction during the sealing operationlimits the accuracy to which reed switches may be made using thistechnique.

Other patents which disclose pertinent prior tech' niques and structureand are thus useful in providing a fuller understanding of this art are:US. Pat. Nos. 2,696,543; 2,978,556; 3,284,876; 3,345,593; 3,369,29l;3,432,282; 3,550,268; 3,568,310; and German Pat. No. 1,904,099; and auseful reference work which provides a comprehensive discussion of reedswitches and their operating characteristics is Designers Handbook andGlossary of Terms relative to reed relays available from MagnecraftCorporation, Chicago, lll.

SUMMARY OF THE INVENTION The present invention discloses and has as aprimary object the provision of a method of precisely positioningelectrical contacts in a sealed enclosure. in the application oftheprinciples of this invention to the manufacture of reed switches, thereed blades are first firmly secured with a fixture in the relativeposition desired for the finished switch. While so constrained withinthe fixture, the reed blades are rigidly joined together by welding anelectrically conductive strap across the two to form a bridge within aregion adjacent the respective confronting active contact areas(contacts), and the strap is thereafter annealed to relieve any internalstresses which may have been caused by the welding operating. Duringwelding and annealing operations care is taken to prevent oxidation ofthe components, inert or reducing gas (such as nitrogen for example) maybe directed towards and over the components during such operations.After removal from the fixture, the reed blades and interconnectingbridge may be handled as an integral assembly during each subsequentproduction step such as cleaning, automatic feeding and the like, andthis assembly is sealed as an integral unit into a glass envelope havinga preferred inert atmosphere. The reed blades precisely retain theirpredetermined relative orientation during the aforesaid sequence ofprocess steps by virtue of the integral substantially rigid assemblyprovided. An electrical current pulse of predetermined magnitude is thenpassed through the assembly from an external source to melt the bridingstrap and thus mechanically disconnect the reed blades in the positioninitially established in the preassembly fixture.

The precise characteristics of the melting current are chosen not onlyto melt the strap, but also to preclude disfiguration of the activecontact areas by the melted matter evaporating and spattering on them.The bridging strap may itself be composed of magnetic material and themelting current pulse selected such that melted material flows andsolidifies on the reeds in the switch ing area (but not on theconfronting contacts) thereby adding a mass of magnetic material toenhance switching performance.

Complex mechanisms for positioning and gapping during the sealingoperation are thus unnecessary, and as a consequence, inaccuracies dueto non-uniform expansion of a positioning mechanism as can occur byprior assembling means, during the sealing operation are virtuallyeliminated. The apparatus required for practice of this invention isinherently simple, particularly since the sealing function has been madeindependent of the gap control function. Volume production of thehighest quality components at minimum cost is thus achieved.

DESCRIPTION OF THE DRAWING The invention will be more fully understoodby reference to the following detailed description when taken inconjunction with the drawing in which:

FIG. 1 is a pictorial view of a reed switch according to the presentinvention;

FIG. 2 is a pictorial view ofa fixing having means for providing precisereed blade alignment and contact gap spacing;

FIG. 3 is a pictorial view of a pair of reed blades held in the fixtureof FIG. 2 by magnetic means, where the reed blade contact overlap isprecisely defined by a removable stop;

FIG. 4 is a pictorial view of a pair of reed blades in a fixture havingan alternative form of reed blade retaining means;

FIG. 5 illustrates a strap welded to the reed blades forming aconductive. rigid bridge across the gap between contact areas;

FIG. 6 illustrates electrical annealing apparatus for relieving strainsin the welded strap;

FIG. 7 shows the glass encapsulated strapped reed blades connected to amelting current source;

FIG. 8A shows a pair of reed blades bridged by an alternative form ofwelded strap;

FIG. 8B illustrates a completed reed switch embodying the reed blade andstrap configuration of FIG. 8A;

FIG. 9A shows another alternative pair of reed blades joined by awelding strap;

FIG. 9B shows a completed reed switch embodying the reed blade and strapconfiguration of FIG. 9A;

FIG. 10A shows still another alternative reed blade and strap structure;and

FIG. [08 illustrates a completed reed switch embodying the reed bladeand strap configuration of FIG. [0A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A normally open reed switchconstructed according to the principles of the present invention isdepicted in FIG. 1. More specifically, a pair of generally flat,magnetic and conductive reed blades 10 and 12 are disposed in closelyadjacent, partially overlapping, spaced relationship within an elongatedsealed enclosure 14 of glass of like material. The reed blade is aunitary or integral structure which may be formed of either a singlemetal or alloy of a composite of differing materials. Typically, thereed blades are formed of a metal suitable for hermetic sealing to glasssuch as a 50-50 nickel-iron magnetic alloy. Alternatively. a compositereed blade structure can be employed having, for example, a Dumetsection for glass sealing and a 70-30 ironnickel magnetic alloy for theblade portion. Reed blades I0 and I2 are formed with integralcylindrical lead portions I6 and 18, respectively, which are hermetically sealed into the ends 20 and 22 of enclosure 14, and serve aselectrical connecting leads for the device. A suitable inert atmosphereis provided within enclosure 14.

The reed blades 10 and I2 are of generally thin, rectangularcross-section, with the overlapping, confronting, flat surfaces at theinner ends thereof constituting electrical contact areas (contacts) 24and 26. The flat portions of the reed blades are flexible and arenormally in the open electrical condition shown. In response to theapplication ofa predetermined solenoidal magnetic field from a source(not shown) the reed blades flex toward each other causing the contacts24 and 26 to close. Metal segments 28 and 30 are shown welded torespective reed blades 10 and 12, the significance of which will bepresently described.

According to the invention, the reed blades are retained as an integralassembly throughout the manufacturing process in a precise spatialarrangement. During an initial step of the manufacturing process, afixture 32 shown pictorially in FIG. 2 is employed to precisely positionthe reed blades in the desired final operating position, for subsequentassembly. Fixture 32 includes first and second pedestals 34 and 36, thelatter being of greater height than pedestal 34 by a predeterminedamount corresponding to the desired gap spacing between contact areas,typically 3-5 mils. A rectangular groove 38 is provided the length ofpedestal 34, while a similar groove 40 is provided in pedestal 36 and inparallel with groove 38. Grooves 38 and 40 are arranged to accommodatethe rectangular reed blades in the manner illustrated in FIG. 3, andwhen inserted, the reed blades are retained therein by action of magnets42 and 44 provided within the respective fixture pedestals 34 and 36. Inthis stage of assembly, the reed blade 10 is butted against the verticalsurface of step 37 of pedestal 36, while reed blade 12 is placed withits inner end extending beyond the step surface an amount governed bythe position of a stop 46. The bar is adjustable laterally as suggestedby double arrow 48 to control the amount of overlap of the confrontingend portions of reed blades 10 and I2, and once the reed blades havebeen properly positioned in fixture 32, stop bar 46 is removed assuggested by arrow 50. The mechanical expedients providing lateraladjustment and pivotal motion of stop 46 are considered within the skillof the art, and have been omitted from the drawing.

An alternate arrangement for maintaining the precise relativedisposition of reed blades 10 and 12 in fixture 32 is depicted in FIG. 4wherein a pair of mechanical clamps 52 and 54 are provided for retainingreed blades 10 and I2 during initial assembly instead of magnets,although both clamps and magnets may be used. The overlap of the reedblades is again defined by a stop (not shown) which may be the same asstop 46 in FIG. 3. Clamps 52 and 54 are pivotable about the axis of asupport rod 56, with respective ends 58 and 60 arranged to press uponrespective reed blades I0 and 12 to retain the physical relationshipshown. As in the case of FIG. 3, this arrangement insures exactalignment. gap spacing, overlap and parallelism of the blade surfaces.

With reference now to FIG. 5. a rigid wire strap 62 of electricallyconductive material is shown welded between reed blades I0 and I2 nearthe respective contact areas thereof. thus electrically and mechanicallybridging the spaced reed blades to form an integral structure whichmaintains the predetermined spaced relationship After welding strap 62into place. but prior to removal from fixture 32 of the integralassembly provided by the bridged reed blades and I2, strap 62 isannealed to relieve the internal stresses therein which might otherwisecause misalignment or distortion ofthe fixed relation of reed blades 10and 12 after removal from the holding fixture. Annealing may beaccomplished as shown in FIG. 6 by connection to annealing currentsource 64 having output leads 66 and 68 connected to terminals 70 and 72which are maintained in good electrical contact with respective reedblades 10 and 12 by a suitable mechanism. A timer 74 is coupled tocurrent source 64 to govern the duration of operation of the latterduring which current is supplied via terminals 70 and 72 to read bladesl0 and 12 and to the interconnected bridging strap 62. Reed blades I0and I2 are firmly held in position by magnets 42 or 44 or the clamparrangements of FIG. 4 during this annealing step. Fixture 32 is of anelectrically insulative material or includes insulation within grooves38 and to confine the annealing current flow to the path provided byreed blades 10 and I2 and strap 62. Due to the smaller cross-section ofthe strap 62, the annealing current pulse, which is of prearrangedmagnitude and duration selectively raises the temperature of the strapto the annealing temperature for the metal used. to relieve all internalstresses and strains.

The integral reed blade assembly accurately maintains the spatialrelationship of the reed blades including the confronting contact areasthereof, and this reed blade assembly can after removal from the fixtureof FIG. 6 be handled during subsequent steps of device fabricationwithout affecting the precise relationship between the first and secondreed blades. Prior to the encapsulation within a sealed glass envelope,the integral reed assembly may be processed through desired ultrasoniccleaning and drying operations, and may be atuomatically machine fedwithout in any way altering the precise and rigidly maintained parallelconfronting relationship of the reed blades and their associated contactareas.

The integral reed blade assembly is then hermetically sealed within aglass envelope I4. If composite reed blades are employed, the envelopeis sealed to the Dumet portion of the reed blades. After hermeticallysealing of envelope I4 to leads I6 and I8, and as a final step in thenovel process, strap 62 is melted to isolate reed blades 10 and I2.Referring now to FIG. 7, the leads l6 and 18 are connected to a meltingcurrent source 88 such as by conductive terminal clips 90 and 92 andinterconnecting leads 94 and 96. Timer 98 controls current source 88 anddetermines the interval during which current is applied through the reedblade and strap assembly. As in the case of the annealing currentdescribed in connection with FIG. 6, the higher resistance of strap 62causes it to heat to a much higher temperature than reed blades 10 and12. The strap melts while the reed blades remain relatively cool, andthus electrically separates the reed blades within the enclosure. Thewelded ends 28 and 30 of strap 62 remain on the reed blades, as shown inFIG. I. The melting of strap 62 electrically isolates the reed blades 10and 12 to provide a normally open reed switch. The glass enclosure andthe respective hermetic glass-to metal seals now permanently retain thereed blades 10 and I2 in precisely the mechanical interrelationshipestablished in the assembly fixture shown in FIG. 5.

The characteristics of the melting current are selected for the strap 62to prevent the melted metal from spattering or evaporating on to thecontacts, which could affect the electrical performance and reliabilityof the completed device.

Noting as in FIG. I, that a portion of each end of strap 62 remains neara respective reed blade contact, performance of the completed switch maybe enhanced by using conductive magnetic material for strap 62. In thismanner welded ends 28 and 30, FIG. I, add to the magnetic mass of thereed blades and aid in the response thereof to an applied solenoidalmagnetic field.

In accordance with this invention, the configuration of the reed bladesand contacts may be varied in form to suit particular needs and toimpart specific characteristics. Alternate reed blade and contactarrangements are shown as examples in FIGS. 8-I0, inclusive. Referringto FIG. 8A. reed blades I00 and 102 are dis posed coaxially with theblade surfaces in parallel and with a conductive strap I04 welded to thereed blades and bridging the space I06 between the reed blade ends.Strap 104 includes an integral contact section I08 which extends a smallpredetermined distance over the inner end portion of reed blade I00 andwhich is spaced therefrom by a selected amount to define the contactgap. A necked-down integral section of element 104 provides a highelectrical resistance. meltable link which is sufficiently rigid toretain the assembly as shown through each process step includingencapsulation of the integral reed blade assembly within an envelope 112as depicted in FIG. 8B. As above, a melting current pulse is used toselectively burn-out the necked-down section 110 to yield the finishedswitch, as in FIG. 8B.

A variation of the reed blade assembly of FIG. 8A is illustrated in FIG.9A wherein reed blades II4 and 116 are again arranged coaxially, with acontact element 118 welded to the inner end of reed blade 116 andextending over the inner end of reed blade I14 and spaced therefrom todefine the contact surfaces and gap. A meltable conductive element I20having a reduced area, high resistance section in the center thereof iswelded between the reed blades as shown. After encapsulation as beforein glass enclosure I22 link I20 is melted by an applied current toisolate the reed blades electrically and complete the switch, as shownin FIG. 9B.

Still another reed blade and strap configuration is shown in FIG. 10A,where a single flexible reed blade I24 is associated with a contactelement 126 conductively attached to lead I28. A wire strap I30 iswelded between the inner end of reed blade I24 and a flat surface onmember I26 to rigidly maintain the desired spaced interrelationship ofthe confronting contact areas during switch assembly. After the integralreed blade assembly is sealed within an envelope 132, as shown in FIG.IOB, strap 130 is melted to electrically isolate the contacts andcomplete the device. In FIGS. 8-10 inclusive. the reed blades aremagnetic as shown in FIG. 1, and the respective straps may also bemagnetic for the advantageous characteristic previously set forth.

It will be appreciated that the invention may be implemented by variousalternative structures utilizing the steps herein set forth to meetspecific requirements. Moreover, the reed switches fabricated accordingto the principles of this invention may be varied. for example, to havedouble pole or double throw action, without departing from the spirit ofthe invention. and generally related electrical devices may be madeembodying the same process techniques. Accordingly, it is not intendedto limit the invention to that which has been particularly shown anddescribed, but only as indicated by the scope of the appended claims.

What we claim is:

l. A method for precisely positioning a pair of coacting conductiveswitch contacts within a scaled enclosure comprising the steps of:

disposing said contacts in a fixed predetermined spatial relationship;

rigidly joining said contacts with an electrically conductive meltableconnection while in said fixed predetermined spatial relationship;

sealing said contacts while joined as aforesaid within an enclosurewhereby said rigid connection retains said contacts in saidpredetermined spatial relationship; and

eliminating said connection between said contacts by melting said rigidconnection within said enclosure.

2. A method for precisely positioning a pair of coacting conductiveswitch contacts within a sealed enclosure in accordance with claim l andincluding:

the step of relieving stresses and strains in said meltable connectionafter rigidly joining said contacts.

3. A method for precisely positioning a pair of coacting conductiveswitch contacts within a sealed enclosure in accordance with claim 1wherein:

said contacts are joined by welding a rigid meltable metal strap acrosssaid contacts; and

an electrical current is directed through said contacts and welded strapto heat and anneal said strap to relieve residual stresses and strainstherein while said contacts remain in said fixed predetermined spatialrelationship.

4. A method for precisely positioning a pair of coacting conductiveswitch contacts within a sealed enclosure in accordance with claim 3wherein:

said contacts when rigidly joined by said welded meltable metal strapare disposed in fixed overlapping relationship in the region of saidstrap.

5. A method for precisely positioning a pair of coacting conductiveswitch contacts within a sealed enclosure in accordance with claim 4wherein:

said contacts, when disposed in said predetermined overlappingrelationship are separated in the region of said overlap to provide agap between the respective confronting surfaces thereof.

6. A method of fabricating an electrical reed switch comprising thesteps of:

disposing first and second electrically conductive,

magnetic reed blades in a fixed predetermined spatial relationshipdefining confronting switch contacts;

rigidly joining said reed blades with a rigid meltable conductive metalstrap while said reed blades are disposed in said fixed predeterminedspatial relationship; relieving stresses and strains in said meltablemetal strap while said reed blades are firmly maintained 5 in said fixedpredetermined spatial relationship thereby providing a self supportingintegral assembly of said reed blades and strap; sealing said integralassembly within a rigid enclosure with selected portions of said reedblades extending outwardly therefrom while said rigid metal strapremains joined to said reed blades entirely within said enclosure; anddirecting an electrical current serially through said reed blades andsaid strap to melt and burn-out said within said sealed enclosure toprovide electrical separation of said reed blades within said enclosure,with said enclosure providing rigid mechanical support for said reedblades; 7. A method of fabricating an electrical reed switch comprisingthe steps of:

disposing and firmly retaining first and second electrically conductive,magnetic reed blades each having a flexible relatively flat spatial andan integral lead portion in a fixed spatiall relationship with said flatportions spaced and overlapping in part to define confronting switchcontacts having a predetermined gap; welding a rigid meltable conductivemetal strap to said reeds across said gap while said reed blades arefirmly retained as aforesaid in said fixed predetermined spatialrelationship; directing an electrical current through ssaid reed bladesand strap to heat and anneal said strap to receive stresses and strainstherein while said reed blades are firmly maintained in said fixedpredetermined spatial relationship, thereby providing a self supportingintegral assembly of said reed blades and strap; hermetically sealingsaid integral assembly within a tubular glass enclosure with said leadportions of said reed blades extending outwardly therefrom while saidrigid metal strap remains joined to said reed blades entirely withinsaid glass enclosure; and

directing an electrical current serially through said reed blades andsaid strap within said sealed glass enclosure to selectively melt andburn-out said strap to provide electrical separation of said reed bladeswithin said glass enclosure, with said glass providing rigid mechanicalsupport for said reed blades.

8. A method for precisely positioning a pair of coacting conductiveelements within a sealed enclosure comprising the steps of:

disposing first and second elements in a fixed predetermined spatialrelationship;

rigidly joining said elements with an electrically conductive meltablestrap while in said fixed predetermined spatial relationship;

sealing said elements while joined as aforesaid within an enclosurewhereby said rigid connection retains said elements in saidpredetermined spatial relationship; and

eliminating said connection between said elements by melting said rigidstrap within said enclosure.

9. A method for precisely positioning a pair of coacting conductiveelements according to claim 8 wherein:

said first and second elements comprise reed blades;

said step of disposing said elements includes the step of positioningsaid reed blades along a common linear axis defining a gap betweenconfronting ends of said reed blades along said common axis; said strapcomprises a contact section attached to one of said reed blades andconfronting a portion of said other reed blade in overlapping spacedrelationship defining confronting switch contacts, and an integral fusesection joining said contact section to said second reed blade; and saideliminating step includes the step of melting said fuse section. 10. Amethod for precise positioning a pair of coactive conductive elementswithin a sealed enclosure according to claim 8 wherein said disposingstep includes LII fronting ends thereof.

1. A method for precisely positioning a pair of coacting conductive switch contacts within a sealed enclosure comprising the steps of: disposing said contacts in a fixed predetermined spatial relationship; rigidly joining said contacts with an electrically conductive meltable connection while in said fixed predetermined spatial relationship; sealing said contacts while joined as aforesaid within an enclosure whereby said rigid connection retains said contacts in said predetermined spatial relationship; and eliminating said connection between said contacts by melting said rigid connection within said enclosure.
 2. A method for precisely positioning a pair of coacting conductive switch contacts within a sealed enclosure in accordance with claim 1 and including: the step of relieving stresses and strains in said meltable connection after rigidly joining said contacts.
 3. A method for precisely positioning a pair of coacting conductive switch contacts within a sealed enclosure in accordance with claim 1 wherein: said contacts are joined by welding a rigid meltable metal strap across said contacts; and an electrical current is directed through said contacts and welded strap to heat and anneal said strap to relieve residual stresses and strains therein while said contacts remain in said fixed predetermined spatial relationship.
 4. A method for precisely positioning a pair of coacting conductive switch contacts within a sealed enclosure in accordance with claim 3 wherein: said contacts when rigidly joined by said welded meltable metal strap are disposed in fixed overlapping relationship in the region of said strap.
 5. A method for precisely positioning a pair of coacting conductive switch contacts within a sealed enclosure in accordance with claim 4 wherein: said contacts, when disposed in said predetermined overlapping relationship are separated in the region of said overlap to provide a gap between the respective confronting surfaces thereof.
 6. A method of fabricating an electrical reed switch comprising the steps of: disposing first and second electrically conductive, magnetic reed blades in a fixed predetermined spatial relationship defining confronting switch contacts; rigidly joining said reed blades with a rigid meltable conductive metal strap while said reed blades are disposed in said fixed predetermined spatial relationship; relieving stresses and strains in said meltable metal strap while said reed blades are firmly maintained in said fixed predetermined spatial relationship thereby providing a self supporting integral assembly of said reed blades and strap; sealing said integral assembly within a rigid enclosure with selected portions of said reed blades extending outwardly therefrom while said rigid metal strap remains joined to said reed blades entirely within said enclosure; and directing an electrical current serially through said reed blades and said strap to melt and burn-out said within said sealed enclosure to provide electrical separation of said reed blades within said enclosure, with said enclosure providing rigid mechanical support for said reed blades.
 7. A method of fabricating an electrical reed switch comprising the steps of: disposing and firmly retaining first and second electrically conductive, magnetic reed blades each having a flexible relatively flat spatial and an integral lead portion in a fixed spatiall relationship with said flat portions spaced and overlapping in part to define confronting switch contacts having a predetermined gap; welding a rigid meltable conductive metal strap to said reeds across said gap while said reed blades are firmly retained as aforesaid in said fixed predetermined spatial relationship; directing an electrical current through ssaid reed blades and strap to heat and anneal said strap to receive stresses and strains therein while said reed blades are firmly maintained in said fixed predetermined spatial relationship, thereby providing a self supporting integral assembly of said reed blades and strap; hermetically sealing said integral assembly within a tubular glass enclosure with said lead portions of said reed blades extending outwardly therefrom while said rigid metal strap remains joined to said reed blades entirely within said glass enclosure; and directing an electrical current serially through said reed blades and said strap within said sealed glass enclosure to selectively melt and burn-out said strap to provide electrical separation of said reed blades within said glass enclosure, with said glass providing rigid mechanical support for said reed blades.
 8. A method for precisely positioning a pair of coacting conductive elements within a sealed enclosure comprising the steps of: disposing first and second elements in a fixed predetermined spatial relationship; rigidly joining said elements with an electrically conductive meltable strap while in said fixed predetermined spatial relationship; sealing said elements while joined as aforesaid within an enclosure whereby said rigid connection retains said elements iN said predetermined spatial relationship; and eliminating said connection between said elements by melting said rigid strap within said enclosure.
 9. A method for precisely positioning a pair of coacting conductive elements according to claim 8 wherein: said first and second elements comprise reed blades; said step of disposing said elements includes the step of positioning said reed blades along a common linear axis defining a gap between confronting ends of said reed blades along said common axis; said strap comprises a contact section attached to one of said reed blades and confronting a portion of said other reed blade in overlapping spaced relationship defining confronting switch contacts, and an integral fuse section joining said contact section to said second reed blade; and said eliminating step includes the step of melting said fuse section.
 10. A method for precise positioning a pair of coactive conductive elements within a sealed enclosure according to claim 8 wherein said disposing step includes positioning said elements along a common linear axis and defining a gap along said axis and between the confronting ends thereof; and including the step of attaching a rigid conductive metal member to one of said elements, said member being disposed across said gap and in overlapping spaced relationship with the other element to define switch contacts.
 11. A method for precisely positioning a pair of coacting conductive elements within a sealed enclosure according to claim 10 wherein said elements are joined by welding a rigid meltable metal strap across the confronting ends thereof. 